Construction of a sensitive cascade catalytic method for measurements of plasma phosphatidylcholine

Abnormal metabolism of phosphatidylcholine (PC) leads to diseases such as cardiovascular, respiratory distress syndrome, chronic inflammatory bowel, and Alzheimer. In this study, we established an efficient colorimetric catalytic cascade system to measure PC value. In the first stage, PC is hydrolyzed to choline and phosphatidic acid by phospholipase D (PLD). Then, choline is used to produce hydrogen peroxide by choline oxidase (ChO). Finally, ABTS (2,2′-Azino-bis(3-ethylbenzthiazoline-6-sulfonic acid)) produces green color in the presence of hydrogen peroxide and deoxyribozyme (DZ). Kinetic study of DZ showed that the value of Km was 0.190 and 0.078 mM for ABTS and hydrogen peroxide, respectively. Assay optimization showed that pH 7.5 and 30 °C were the best conditions for the sensing of PC. In addition, 0.075 μM DZ, 0.16 U/mL ChO, and 12 U/mL PLD were the best concentration for PC detection. The interfering study revealed that the constituents had no apparent absorbance value. The linear regression equation for PC was identified as A = 0.0052C + 0.0233 with a correlation coefficient of 0.9923. The limit of detection of this catalytic cascade system was obtained as 0.58 μM. PC evaluation in serum samples showed that the mean percentage recovery of PC was 97.98%. Taken together, good recovery and precision of PC detection designated that this colorimetric sensing approach is applicable for PC detection in real samples.